Futures contracts based on carbon permits for 2013, the first year of compliance under the program, fell 25 cents to $12.15 a metric ton yesterday, according to data compiled by CME Group Inc. (CME)’s Green Exchange in New York. Permits are down 40 percent from this year’s high of $20.25 on July 24.

“Conservatives are utterly naive to believe that they will get trade-offs in response to a carbon tax,” Kenneth Green, a resident scholar at AEI, said in an interview. “We’ve had some robust discussions over the lunch table about our differences.”